Embodiments relate to refrigeration equipment. More specifically, embodiments relate to a vehicle refrigerator having a liquid line sub-cooled vapor cycle system.
Conventional refrigeration units for chilling food and beverages used in vehicles such as aircraft and other galley food service systems include vapor cycle systems that use a fluid refrigerant to chill air for circulation in a compartment that stores food and beverages. In general, vapor cycle systems for refrigeration units are designed to maintain set temperatures as required for steady state heat loads. However, when a refrigeration unit is first turned on to chill food and beverages, the heat load is much larger than steady state because the temperature in the compartment holding the food and beverages must typically be pulled down by a large amount, for example from an ambient air temperature (e.g., 72 degrees Fahrenheit (F)) to a refrigerator or freezer temperature (e.g., 39 degrees or 0 degrees F.). It is generally desirable for the temperature to be pulled down as quickly as possible so that the food and beverages are at an ideal serving temperature shortly after being loaded on the vehicle in preparation for embarking on a journey.
However, in order for a conventional vapor cycle system to pull down the temperature more quickly, the components of the vapor cycle system would need to be made larger and heavier. Increasing the size and weight of the components is in conflict with the need for systems onboard vehicles such as aircraft to be made smaller and lighter in order to save space and weight, and reduce total life cycle costs including fuel consumption. Therefore, there is a need to increase the cooling capacity of vapor cycle systems of refrigeration units for vehicles to increase the speed with which the temperature of food and beverage compartments can be pulled down without significantly increasing the size and weight of the refrigeration units.